Non-linear optical component

ABSTRACT

A non-linear optical component for use in laser systems providing frequency conversion, detection and modulation of electromagnetic radiation. The component is a monocrystal of barium nitrite hydrate, (Ba(NO2)2. H2O) and includes a pair of electrodes mounted on opposite surfaces of the component.

\ United States Patent [1 1 [111 3,830,558 Deserno et a1. Aug. 20, 1974 1 NON-LINEAR OPTICAL COMPONENT [75] Inventors: Ulfici Desernmfiiini hi e ces Ci ed Siegfried Haussuehl, Cologne, both UNITED STATES PATENTS of Germany 3,457,417 7/1969 Buchsbaum 331/945 N X l [73] Assignee: Siemens Aktiengesellschaft, Berlin & 3,586,997 6/1971 Kinsel 331/945 M Munich, Germany Prima Examiner-John K. Corbin 22 1 d: 1 Fl e Feb 14 1973 Assistant Examiner-Paul K. Godwin [21] Appl. No.: 332,312 Attorney, Agent, or Firm-Hill, Gross, Simpson, Van

Related Us. Application Data Santen, Steadman, Chiara & Simpson [63] Continuation-impart of Ser. No. 234,970, March 15,

1972, abandoned. [57] ABSTRACT A non-linear optical component for use in laser sys- [30] Foreign Application Priority Data terns providing frequency conversion, detection and Mar. 26,1971 Germany 2114823 modulation of electromagnetic radiation The component is a monocrystal of barium nitrite hydrate, [Ba(- [52] US. Cl 350/160, 307/88.3, 331/945 N N() H 0] d i ludes a pair of electrodes [51] Int. Cl. G02f l/40 t d on pp site surfaces of the component. [58] Field of Search 307/88.3; 350/160 R; o

331/945 M, 94.5 N 5 Claim 3 Drawmg Flgms I a 2, 7 2 XU )H c005,? AND MOD AMPL/FIEIR DECODER l NON-LINEAR OPTICAL COMPONENT CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of US. Ser. No. 234,970, filed Mar. 15, 1972, now abandoned and which is incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to non-linear optical components and more particularly to monocrystal non-linear optical components for electro-magnetic radiation in infra-red, visible and ultra-violet spectrum range.

2. Prior Art Single crystals having non-linear dielectric properties are known for frequency control, such as production of frequency-doubled radiation. Examples of such crystals include ammonium dihydrogen phosphate (ADP), potassium dihydrogen phosphate (KDP) or lithium niobate (LiNbO and they are characterized by dielectric constants that are a function of the strength of an applied electrical field. When a light of a given frequency is radiated into such a crystal, i.e., at the so-called fundamental wave frequency, light with frequencies that are harmonics of such frequency is obtained on the side of the crystal where the light emerges. However, prior art monocrystals lack efficiency.

SUMMARY OF THE INVENTION The invention provides a non-linear optical component for electro-magnetic radiation in the infra-red, visible and ultra-violet spectrum range comprised of a monocrystal consisting essentially of barium nitrite hydrate. In preferred embodiments, the monocrystal component of the invention is provided with opposed electrodes for applying controlled voltage to the component. The optical component of the invention is useful in laser systems as a frequency converter, such as a phase-matched frequency-doubling component, a frequencymixing component or a parametric frequency converting component, the component is also useful as a modulating device or as a detection device in optical or electro-optical systems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevated perspective view of the invention;

FIG. 2 is a schematic view of a laser communication system utilizing the monocrystal component of the invention for frequency modulation; and

FIG. 3 is a schematic view of a laser system utilizing the optical component of the invention for frequencydoubling.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention provides a non-linear optical component for electro-magnetic radiation in the infra-red, visible and ultra-violet spectrum range. The component is a mono or single crystal consisting essentially of barium nitrite hydrate [Ba(NO;),'I-I,O] and is characterized by an improved efficiency in light or electromagnetic radiation control in relation to prior art monocrystals.

In preferred embodiments, the non-linear optical component of the invention is provided with a means for applying a voltage thereto. In certain preferred forms, such means comprise a pair of electrodes mounted on opposing surfaces of the monocrystal component of the invention.

The monocrystal non-linear optical component of the invention is useful in various optical or electrooptical systems, such as in laser systems, as a frequency converting component, for example, a frequencydoubling component, a phase-matched frequencydoubling component, a frequency-mixing component or a parametric-frequency converting component for electro-magnetic radiation in the infra-red, visible and ultra-violet spectrum range. The non-linear monocrystal Optical components of the invention is also useful in operational electrooptical systems as a modulating component for electrO-magnetic radiation.

Further, the non-linear monocrystal optical component of the invention is also useful in operational electro-optical systems as a detection component for electro-magnetic radiation.

[Ba(NO H O] monocrystals have high non-linear tensor components for dielectric susceptibility. Such monocrystals also have the required optical characteristics, such as anistropy and dispersion necessary for phase-matching of primary and secondary electromagnetic waves. Thus, the [Ba(NO,) H O] crystals of the invention are useful for phase-matched frequencydoubling, frequency-mixing and parametric-frequency conversion of electro-magnetic' radiation with a high degree of efficiency. The phase adjustment is effected by the crystal in such a way that the dispersion occurring between the fundamental wave (or frequency) and a harmonic thereof is compensated by means of a suitable adjustment in the refraction-index difference between these waves. The refraction-index difference between a basic wave and a harmonic thereof occurs when the electric vector of both waves are orientated differently with respect to the crystal-coordinate system, apparently due to the optical anistropy of the crystal Monocrystals composed of [Ba(NO,) H O] are readily produced by conventional processes, such as by slow evaporation of an aqueous solution containing [Ba(NO,) H 0] and a gradual lowering of temperature so'that a desired monocrystal is attained. Once a suitable sizecrystal is attained, it is preferable to cut and polish the crystal surface in a conventional manner to attain a useful optical component.

FIG. 1 illustrates a [Ba(NO I-LO] monocrystal or single crystal 11. An electrode 2 is provided on one surface thereof. A similar electrode (not shown) is provided on the Opposing surface thereof. Conducting means 3 and 4 are operationally connected to the electrodes for communicating an electrical signal from a voltage source (not shown) so that a select signal can be applied to the component 11.

An adjustment of the refraction-index difi'erence is readily effected by various means, for example, by totating the monocrystal so that the angle orientation of the beam in respect to the optical axes of the monocrystal is changed; by an electro-optical effect, i.e., by applying a voltage to the crystal; by a piezo-optical effeet; or by a temperature change.

The excellent transparency characteristics of the barium nitrite hydrate monocrystal optical component provided by the invention extends far beyond the visible spectrum range and allows such crystal to also have utility in the ultra-violet and infra-red spectrum range. in addition to frequency-doubling, frequency-mixing and parametric-frequency conversion, the monocrystal optical components of the invention are also useful in electro-optical systems for modulation, detection and- /or deflection of electro-magnetic radiations in an operational optical or electro-optical system.

FIG. 2 illustrates an exemplary laser communication system 20, which includes the non-linear optical component ll of the invention. The laser system 20 includes a gas discharge tube 21, which when operating provides optical radiation and a pair of mirrors 21A and 21B positioned to form an optical resonator, with mirror 21B allowing some radiation to pass the-rethrough in a conventional manner. The optical component 1] is positioned to receive the optical radiation passing through mirror 218. An electrically modulated signal is supplied to electrodes 2 and 2A positioned in working relation to opposing surfaces of component 11 via conduits 3 and 4 from a suitable coder and modulation amplifier 31. The electrical signal causes component 11 to modulate the frequency of the optical radiation passing through its body. The modulated frequency is received by a photo-electric demodulator 41 and may be reconverted into electrical signals by de coder 42.

FIG. 3 illustrates an exemplary laser system 30 useful in experimental work for frequency-doubling process or phase-matched frequency-doubling by altering the initially produced optical radiation with the non-linear optical component 11 of the invention. The laser system 30 includes a gas discharge tube 22, which when operating provides optical radiation and a pair of mirrors 22A and 22B positioned to form an optical resona' tor. A monocrystal optical component 11, composed of [Ba(NO H O] is interposed between the discharge tube 22 and mirror 228. A modulating voltage source 51 supplies a modulating voltage to electrodes 2 and 2A, which may be attached to opposing surfaces of component 11 via conduits 3 and 4 or may be spaced therefrom. The pulsed fundamental wave produced by tube 22 is increased, as in frequency-doubling. The modulating voltage on component 11 produces a harmonic of the fundamental wave and it can be collimated and is coherent to the same extent as the fundamental wave.

Other laser systems for utilizing the optical monocrystal component of the invention are also known; for example, see D. Roess Lasers, Light Amplifiers and Oscillators (1969), Academic Press Publishing Co., London and New York; U.S. Pat. Nos. 3,422,370; 3,457,417 or 3,508,164; all of which are incorporated herein by reference as shown useful systems that may We claim as our invention:

1. A non-linear optical component for frequency control of electro-magnetic radiation in the infra-red, visible and ultra-violet spectrum range comprising a monocrystal composed of barium nitrite hydrate and means for changing the optical properties of said monocrystal.

2. A non-linear optical component as defined in claim 1 wherein said means includes a pair of electrodes, each mounted on an opposing surface of said monocrystal.

3. In a laser system including means for producing electro-magnetic radiation in the infrared, visible and ultra-violet spectrum range and a means for frequency control of said electromagnetic radiation, the improvement comprising that said means for frequency control comprises a non-linear monocrystal optical component composed of barium nitrite hydrate.

4. A method of obtaining a harmonic frequency of a basic frequency of electromagnetic radiation in the infrared, visible and ultra-violet spectral region comprismg:

projecting electromagnetic radiation of a basic frequency through a non-linear optical component having a monocrystal composed of barium nitrite hydrate which emits a harmonic frequency of said basic frequency.

5. A method of controlling a beam of electromagnetic radiation in the infrared, visible and ultraviolet spectral region comprising:

projecting a beam of electromagnetic radiation through a non-linear optical component having a monocrystal composed of barium nitrite hydrate; and

changing the optical properties of said monocrystal by applying a voltage to electrodes disposed on said monocrystal so that the characteristics of said beam are changed in response to the changes in the optical properties of said monocrystal. 

2. A non-linear optical component as defined in claim 1 wherein said means includes a pair of electrodes, each mounted on an opposing surface of said monocrystal.
 3. In a laser system including means for producing electro-magnetic radiation in the infrared, visible and ultra-violet spectrum range and a means for frequency control of said electro-magnetic radiation, the improvement comprising that said means for frequency control comprises a non-linear monocrystal optical component composed of barium nitrite hydrate.
 4. A method of obtaining a harmonic frequency of a basic frequency of electromagnetic radiation in the infrared, visible and ultra-violet spectral region comprising: projecting electromagnetic radiation of a basic frequency through a non-linear optical component having a monocrystal composed of barium nitrite hydrate which emits a harmonic frequency of said basic frequency.
 5. A method of controlling a beam of electromagnetic radiation in the infrared, visible and ultraviolet spectral region comprising: projecting a beam of electromagnetic radiation through a non-linear optical component having a monocrystal composed of barium nitrite hydrate; and changing the optical properties of said monocrystal by applying a voltage to electrodes disposed on said monocrystal so that the characteristics of said beam are changed in response to the changes in the optical properties of said monocrystal. 